National Conference on Women & HIV(internet-link: "http://www.womenhivconf.org/") Pasadena, CA, May 4-7, 1997

The protective effect of condoms and nonoxynol-9 against HIV infection

WITTKOWSKI, Knut M. ,*/** DIETZ, Klaus

* Department of Medical Biometry Eberhard-Karls-University Tübingen, Germany,
** HIV Center for Clinical and Behavioral Studies(internet-link: "http://www.nyspi.cpmc.columbia.edu/NYSPI/PIDPT_HV.HTM") NYS Psychiatric Institute(internet-link: "http://www.nyspi.cpmc.columbia.edu") and Center for Urban Epidemiologic Studies, NY Academy of Medicine(internet-link: "http://www.nyam.org/") New York, NY

Keywords: HIV, AIDS, heterosexual, microbicide, N9, nonoxinol, condom

Objective: Even with the new results from the comparison of N9 vs. placebo available (Weir, this conference), the former Cameroon study [5] still is the only source where the efficacy of both condoms and spermicides against HIV transmission can be assessed in a comparable setting. In the present paper, we will explain the seeming inconsistencies in [1] and provide estimates for the effectiveness of each barrier method (condoms and spermicides) per contact.

Methods: We will (1) concentrate on the 224 women with at least one follow up, including two early seroconverters, (2) analyze the number of contacts in each protection class (none, condoms, spermicides alone) rather than few categories of protection and (3) define both condom and spermicide use with comparable denominators. We will use both maximum likelihood estimates and marginal likelihood rankings [2,4] for comparison of efficacy.

Results: HIV transmission decreases with increasing levels of both condom and spermicide use. By maximum likelihood, the risk of unprotected sex is estimated as 0.4%, the efficacy per contact of condoms and spermicides as 89% and 100%, respectively. Using spermicides in combination with condoms did not increase efficacy, indicting that spermicides, when used in combination with condoms might be inserted too late. By marginal likelihood, spermicide use is more effective than condom use among consistent users of either barrier method.

Discussion and Conclusions: Due to limitations in the statistical method used, no estimate of the degree of protection was given in [1,5]. The current reanalysis explains some of the seemingly inconsistencies as artifacts and demonstrates spermicides to be more effective than condoms in vivo [6] . These observations are in accord with earlier estimates based on contraception studies, [3] where efficacy of condoms and suppositories (Pearl index >6 and <2, respectively) had been estimated as above 95% and 99%, respectively.

  1. FELDBLUM PJ, WEIR SS (1994) The protective effect of Nonoxynol-9 against HIV infection. Am J Public Health 84
  2. SUSSER E(internet-link: "http://cait.cpmc.columbia.edu/research/faculty/facu0330.html") DESVARIEUX M, WITTKOWSKI KM (1997) Reporting sexual risk behavior for HIV: a practical risk index and a method for improving risk indices. Am J Pubic Health (in press)
  3. WITTKOWSKI KM (1989) [Assessing the effectivity of barrier methods for HIV prevention AIDS-Forschung 4
  4. WITTKOWSKI KM (1992) An extension to Wittkowski. J Am Statistical Association 87
  5. ZEKENG L, FELDBLUM PJ, OLIVER RM, KAPTUE L (1993) Barrier contraceptive use and HIV infection among high-risk women in Cameroon. AIDS 7
  6. WITTKOWSKI KM (1997) The efficacy of nonoxynol-9 from an in vivo point of view. AIDS 11

Knut M. Wittkowski, PhD, DSc
Center for Urban Epidemiologic Studies, NY Academy of Medicine,
1216 5th Ave, New York, NY, 10029-5293
Fax: 1(212) 876-6220; email: kmw@uni-tuebingen.de(kmw@uni-tuebingen.de)

This work was supported by dfg Wi 827/7-1 grant. The authors would like to thank Paul Feldblum and Sharon Weir for providing the data and assisting in its interpretation.

Other publications on HIV and AIDS

Additional publications and presentation of Knut M. Wittkowski

©1997 Knut M. Wittkowski (kmw@uni-tuebingen.de(kmw@uni-tuebingen.de) Last Updated: 97-05-11 20:27



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National Conference on Women & HIV(http://www.womenhivconf.org/)

HIV Center for Clinical and Behavioral Studies(http://www.nyspi.cpmc.columbia.edu/NYSPI/PIDPT_HV.HTM)

NYS Psychiatric Institute(http://www.nyspi.cpmc.columbia.edu)

NY Academy of Medicine(http://www.nyam.org/)

SUSSER E(http://cait.cpmc.columbia.edu/research/faculty/facu0330.html)